SPOILERS ALERTMatthew Vaughn and a superb cast reinvigorated the franchise with cool retro style and globe-trotting intrigue in 2011's X-Men: First Class. The series' original director, Bryan Singer, continues that momentum in the vigorously entertaining X-Men: Days of Future Past. While it's more dramatically diffuse than the reboot and lacks a definitive villain, the new film is shot through with a stirring reverence for the Marvel Comics characters and their universe. And it ups the stakes by threatening nothing less than the genocide of the mutant population, among them faces old and new.

Hardcore followers will have a geek field day dissecting the challenging pretzel logic of writer-producer Simon Kinberg's screenplay, from a story by Jane Goldman, Kinberg and Vaughn, who had originally planned to direct. The central premise comes from the 1981 Uncanny X-Men comic Days of Future Past, in which Kitty Pryde (Ellen Page) uses her consciousness transference powers to go back from a dystopian future and rewrite history.

Echoes of the Holocaust have rippled throughout the series, and Singer opens with present-day scenes of a desolate, burnt-out New York, where mutants and mutant-sympathizing humans have been rounded up in internment camps.

Jumping to a similarly devastated Moscow, we watch Kitty, Iceman (Shawn Ashmore) and a small band of mutants face an attack from the deadly Sentinels. Dropped in from airborne carrier ships, these robots are designed to track and destroy the mutant gene. They resemble towering, muscular versions of the aliens from Close Encounters of the Third Kind, constructed out of magnetic plates that allow them to change shape and adapt to whatever force is unleashed against them.

The mutants escape and regroup in the rubble of an ancient Chinese monastery with Professor X (Patrick Stewart), Magneto (Ian McKellen), Wolverine (Hugh Jackman) and Storm (Halle Berry). The movie is missing an explanation of how traditional adversaries Professor X and Magneto reached a collaborative truce. But within the elastic boundaries of comic-book mythology that seems no big deal, and it's nice to see their bromance rekindled.

Threatened with extinction, the mutant holdouts hatch a plan to return to the post-Vietnam Paris Peace Accord of 1973, when Mystique (Jennifer Lawrence) killed Dr. Bolivar Trask (Peter Dinklage), a U.S. military scientist developing the Sentinels program. Mystique was captured and experimented on, with the transformative powers of her DNA tapped to perfect the Sentinels.

Wolverine's ability to heal makes him the only one able to withstand the 40-year time jump. Kinberg's script milks welcome humor out of sending the least diplomatic of the X-Men back to convince the younger Professor X (James McAvoy) and Magneto (Michael Fassbender) to join forces and stop the assassination that triggered anti-mutant hysteria. Having Wolverine awaken on a waterbed staring at a lava lamp and listening to Roberta Flack lightens the mood at just the right moment.

Looking Christ-like with his '70s mop and scruffy beard, McAvoy's Charles Xavier couldn't be less like that of Stewart, with his steely but benevolent authority. Disillusioned, Charles is addicted to a serum produced by Beast (Nicholas Hoult) that gives him the use of his legs but strips him of his telepathic powers. Professor X is the one character whose younger and older selves actually meet, in a scene that is among the movie's most emotionally resonant.

There are also affecting moments when Wolverine encounters Major Bill Stryker (Josh Helman), triggering traumatic flash-forward memories of his painful physical transformation and his love for Jean Grey.

Perhaps the film's standout sequence features the much-discussed new addition of Peter Maximoff, aka Quicksilver (American Horror Story regular Evan Peters). The rights dispute that kept the character out of previous films has been resolved, allowing him to appear in both the X-Men and Avengers franchises, albeit without cross-referencing. His super-speed skills are conveyed by shooting at 3,000 frames per second, notably when Peter runs around the walls during a fabulously staged Pentagon break-in, whimsically accompanied by Jim Croce singing Time in a Bottle. With his silver shag, Pink Floyd T-shirt and mischievous sense of humor, Peter is a terrific character who breathes playfulness into the movie, and many will be sorry he doesn't stick around longer.

Fassbender's young Erik/Magneto was the revelation of First Class, and the actor again shows riveting self-possession and charisma to burn - not least when he's standing astride the roof of a moving train in bellbottoms while tearing up railway tracks. But this movie belongs to Jackman and Lawrence.

Logan/Wolverine has possibly never been more compelling. In his seventh turn in the role, Jackman brings powerful physicality, laconic humor and depths of sorrow beneath his gruffness that make him an unusually nuanced figure for a sci-fi action movie.

Switching from her honorable Hunger Games heroine into badass mode with supreme ease, Lawrence is sensational, whether slinking around in Mystique's body-hugging blue reptilian skin, displaying the shape-shifter's balletic fight skills or adopting seductive human form. Her romantic friendship with Charles, stretching back to their childhoods, adds poignancy to Mystique's struggle, notably in a wonderful airport scene during which Professor X gets inside her head via random people in the terminal.

It's hard to imagine fanboys having too much to grumble about here, as Singer has pulled together an ambitious, suspenseful screen chapter that secures a future for the franchise while facilitating continued reinvention. Audiences should sit tight through the end credits crawl for an enigmatic signoff scene that provides a taste of the next installment, X-Men: Apocalypse.